1. Field of the Invention
The invention relates to turbine driven pumps of the type employed to pump fluid from oil wells, particularly oil wells containing significant amounts of gas in the fluid to be pumped.
2. Description of the Prior Art
Turbine driven pumps have long been employed for the pumping of oil wells through the utilization of the energy transmitted to the bottom of the well by a pressurized power fluid produced at the well head. In prior art units, the turbine section of the pump was necessarily designed to operate at a compromise efficiency in order to permit a substantial increase in speed of the turbine when the density of the fluid to be pumped decreased sharply due to the presence of gas. For example, the turbine and pump would be designed to accommodate a speed increase on the order of eight to one which would be produced by a density reduction on the order of sixty-four to one when a substantial amount of gas was present in the pumping fluid. While the efficiency under these gassy conditions is acceptable, being on the order of forty percent, the majority of the operation of the pump when little gas is present is at a much lower efficiency, for example less than thirty percent. The undersirability of operating the pump for long periods of time at such a low efficiency is self-evident.